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KIN365 Exam 1 Review

by: Jess Snider

KIN365 Exam 1 Review KIN 365

Jess Snider

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Powerpoint review for exam 1
Applied Biomechanics
Colleen Geary
Study Guide
KIN365, Exam 1, review
50 ?




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This 63 page Study Guide was uploaded by Jess Snider on Tuesday February 16, 2016. The Study Guide belongs to KIN 365 at University of Alabama - Tuscaloosa taught by Colleen Geary in Spring2015. Since its upload, it has received 90 views.


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Date Created: 02/16/16
KIN365 EXAM REVIEW Exam: 2/18/2016 Muscle & Nerve Phys. ◦ Muscle Types: ◦ Skeletal Muscle: ◦ Smooth ◦ Over 600 responsible for movement of ◦ Cardiac body & joints ◦ Skeletal (the one we cover) ◦ Skeletal muscle roles ◦ Movement: perform opposite joint actions ◦ Protection ◦ Posture & support ◦ Produce body heat: using muscle causes sweating(shivering involuntary ◦ Striated muscle tissue ◦ Voluntary control(somatic) ◦ Individual fibers ◦ Attaches to bone by tendons Skeletal Muscle: structure &function ◦ Tendons: ◦ Three Types of Mysium ◦ Flexible but inelastic cord of fibrous ◦ Epimysium collagen tissue ◦ Surrounds entire muscle & holds it together ◦ No blood supply cannot heal themselves ◦ Outer most layer ◦ Attaches muscle to bone ◦ Perimysium ◦ Allows for movement @ joint ◦ Surrounds group of muscle fibers(fasciculi) ◦ Come from all 3 mysium ◦ Middle layer ◦ Endomysium ◦ Surround individual muscle fibers ◦ Inner most layer ◦ Surrounds: ◦ Sarcoleema: cell or plasma membrane ◦ Sarcoplasm: fluid inside cell or cytoplasm ◦ Muscle cell: contains myofibers ◦ Myofibers made up of myofibrils composed of chain of sarcomeres Sarcomere ◦ Myosin ◦ Sarcomere st ◦ Muscular & thick; makes 1 move ◦ Smallest functional unit of muscle ◦ Contains myosin heads which protrude ◦ Within each myofibril there are 2 type of ◦ Causes binding with actin small protein filaments responsible for muscle action ◦ Forms cross-bridge ◦ Myosin ◦ Interact during muscle action with actin ◦ Actin active sites ◦ Where the striation appearance occurs ◦ Actin ◦ Thin filament ◦ Made up of: ◦ Actin molecules ◦ Troponin ◦ Tropomyosin ◦ during rest stagef actin with myosin ◦ Prevents constant contractions Sliding Filament theory ◦ Cycle of repetitive events that cause the thin, actin filament to slide over the thick, myosin filament to generate tension in the muscle ◦ Res ◦ Excitation-Coupling ◦ Contraction ◦ Recharging ◦ Relaxation ◦ Initiated by action potential ◦ Action potential: ◦ Stimulates the opening of calcium channels ◦ Opening allows for inflow/outflow of calcium which play a hugely important role in muscle contractions Rest ◦ Myosin cross bridge has ATP at tip ◦ ATP binds to myosin & is hydrolyzed by ATPase into ADP & phosphate ◦ Energy released by this process activates myosin head & cocks it into high-energy, extended position ◦ Myosin cross bridge is not attached ◦ Tropomyosin & troponin are blocking active actin binding sites because the calcium ions have not flooded in ◦ Myosin is not attached to actin filaments… preventing binding of the 2 filaments Excitation-Coupling ◦ Calcium ions flood in & attach to troponin actin molecule ◦ Unblocks binding site on action ◦ Results in excitation ◦ Actin filament shifts & changes shape in anticipation of myosin attachment ◦ Myosin heads bind to newly exposed active site on actin filament ◦ Results in Coupling: cross-bridge between myosin & actin formed ◦ Myosin is now attached to actin molecule Contraction ◦ Myosin releases the ADP & phosphate & returns to low energy in position ◦ As ATP is released, myosin pulls thin, actin filament dragged to new location results in Power stroke ◦ Myosin cross bridge changes shape ◦ Shortens sarcomere, drags the Z line to the M line Recharging ◦ A new ATP molecule is put back on the tip of myosin cross-bridge ◦ If this does not happen, the myosin will not let go of action (muscle cramping) ◦ Myosin detaches from actin ◦ If actin binding sites are still available, myosin can bind again with actin Relaxation ◦ When action potentials stop arriving ◦ Calcium releases stops & calcium floods away ◦ Due to motor nerve impulses ◦ Binding sites on actin close, myosin can no longer achieve strong binding ◦ Cross-bridge is prevented ◦ Relaxation of muscle is achieved passively Action Potential ◦ Electrical signal from brain & spinal cord which travels to muscle by way of efferent(motor) nerves signaling the particular motor unit(s) to contract ◦ Initiates the excitation-coupling of myosin & actin during sliding filament theory ◦ Stimulating the voltage- gated calcium channels to open ◦ Stimulus must be strong enough to cause muscle fiber contraction Action Potential Strength ◦ Levels of Strength ◦ Subthreshold: not strong enough to produce action potential in one motor unit ◦ Threshold: strong enough to produce action potential in one motor unit ◦ Submaximal: strong enough to produce action potential in additional motor units ◦ Maximal: strong enough to produce action potential in all motor units of particular muscle ◦ Arrival of single action potential produces a weak brief action of fiber twitch ◦ Not very useful ◦ Producing strong contraction can be accomplished in two ways: ◦ Increase the number of fibers contracting ◦ Increasing frequency of motor unit activation within single fiber ◦ Sending multiple action potentials to muscle fiber Frequency of motor unit ◦ Greater contraction force can be generated by increasing frequency of motor unit activation ◦ Frequency of motor unit activation of single fiber follows: ◦ Latent period: few milliseconds; no change in muscle fiber length ◦ Contraction phase: 40 milliseconds; muscle fiber begins to shorten ◦ Relaxation phase: 50 milliseconds; muscle fiber begins to lengthen back out ◦ Summation: occurs when successive stimuli are provided before the relaxation phase of the 1 twitch st is complete ◦ Subsequent twitches combine with 1 to produce sustained contraction ◦ Equals generation of greater tension than a single contraction would produce initially ◦ As frequency of stimuli increase, the resultant summation increases accordingly producing increasingly greater total muscle tension ◦ Tetanus: occurs if the stimuli are provided at a frequency high enough that no relaxation of the muscle fiber can occur between contractions ◦ Treppe: occurs when multiple maximal stimuli are provided at a low enough frequency to allow complete relaxation between contractions to rested muscle ◦ Slightly greater tension is produced by thestimulus than with the 1 ◦ 3 rgreater stimulus produced even greater tension than the 2 Muscle Contraction ◦ Afferent(sensory) nerves ◦ From muscle to brain ◦ Sends information from muscles to CNS ◦ Efferent(motor) nerves ◦ From brain/spinal cord to muscle ◦ Tell muscles to contract ◦ Somatic Motor Neuron ◦ Nerve cell that processes & transmits information from CNS to muscle ◦ Composed of: ◦ Dendrite ◦ Cell Body ◦ Axon-with myelin sheath ◦ Myelin ◦ Fatty substance wrapped around axon ◦ Speeds up rate of conduction of neurons ◦ Prevents signal decay Motor Neuron/ Nerve Supply ◦ Nerve cells that process & transmits information to directly or indirectly control muscle, including skeletal muscle ◦ Signaled motor neuron may innervate (communicate with) with or many muscle fibers ◦ The motor neuron & all of the muscle fibers which it innervates motor units ◦ Muscle fiber may undergo many action potentials during contraction ◦ Neuromuscular Synapse/Junction ◦ Connects the nervous system of the muscular system ◦ Located at the end of the motor neuron ◦ Allows for the motor nerves to communicate with or innervate muscle fibers Irritability/Excitability ◦ The sensitivity or responsiveness of a muscle to a stimulus-either chemical, electrical, or mechanical ◦ I.e. muscles are considered irritable because can receive & respond to a signal ◦ Without irritability/excitability, muscles wouldn’t fire no movement ◦ Allows for ALL OTHER neuromuscular functions of muscle including contractibility, extensibility, & elasticity Contractility ◦ The ability of muscle to change shape, contract (shorter & thicker), & develop tension or internal force against resistance, IF appropriate stimulus if provided (action potential) ◦ Muscles can develop tension ◦ Property is unique to skeletal muscle ◦ Allows for muscle contractions, tension development, power production which lead to strength & endurance Extensibility ◦ Ability of a muscle to be passively stretched & extended beyond its normal resting length ◦ Can stretch a muscle & all that runs through it ◦ Allows for contractibility & flexibility ◦ Ex: triceps brachii stretched beyond normal resting length when elbow flexors contract to achieve full elbow flexion Elasticity ◦ Ability of a muscle to return to its original or normal resting length following a stretch ◦ Once stretched, a muscle will spring back into original position ◦ Think bubble gum vs. rubber band ◦ Muscle is more like a rubber band ◦ Allows for flexibility Flexibility Endurance ◦ Muscle can stretch through a small or ◦ the ability of the muscle to exert tension over large range of motion time ◦ Dependent on the joint ◦ The longer the tension is exerted, the greater the endurance ◦ Being flexible @ one place, doesn’t mean ◦ Repeated submaximal force development you are flexible elsewhere ◦ Measured over time or by the number of reps can do at certain submaximal amount of force ◦diameter, as training for strength doesuscle fiber ◦ for females  no bulking uperred method of training ◦ Uses slow twitch muscle fibers (won’t fatigue quickly) ◦ Factors that affect strength: ◦ Training state of muscle Strength ◦ With both concentric & eccentric strength training, gains in strength over approximately 1 12 weeks appears to be related to neuromuscular adaption, & not increase in cross-sectional area ◦ Neuromuscular adaptation: the improved innervation of the trained muscle, includes: ◦ The component of muscle force that produces torque @ the joint ◦ Increased neural firing rates ◦ Increased excitability ◦ Measured as a function of the collective ◦ Increased levels of motor output from the CNS force-generating capability of a given (more action potentials sent through efferent functional muscle group pathways) ◦ Maximal force can produce @ one period of time ◦ Muscle cross-sectional area ◦ Relates to tension-generating capabilities of muscle with one muscle or muscle group ◦ Measure with 1 rep max=1 rep @ maximal weight ◦ Occurs beyond 1 12 weeks of strength training ◦ Force Arm ◦ Distance between muscle attachment to bone & joint center ◦ Angle of muscle attachment to bone ◦ Maximum when muscle is oriented @ 90˚ angle to the bone with a change in the angle of the orientation in either direction progressively diminishing the amount of force produced Work ???????????????????? ∗ ???????????????????????????????????????????????? Power ???????????????????? = = Time ???????????????? ◦ Factors that affected power: ◦ Muscle power ◦ Muscular strength (force production @ muscle) ◦ =work or force*velocity ◦ Movement speed (velocity) ◦ =work*velocity ◦ Important for anaerobic activities that requir◦ Can also describe power as how long it takes to explosive movements, such as Olympic develop force weight lifting, throwing, jumping, sprinting ◦ Can develop a great deal of force in a short ◦ FT muscle fibers are asset for individuals trainingunt of time= large amount of power for power (FGF) ◦ Muscle Power: force production per unit time ◦ The rate at which work is performed ◦ How quickly can you generate a lot of force ◦ The product of muscular FORCE & the ◦ Two important factors: VELOCITY of muscle shortening ◦ Force of contraction ◦ The rate of force or torque production at joint ◦ Velocity of movement (time) ◦ Power= force*velocity (P=f*v) Power cont. ◦ With relation to concentric contraction: ◦ Force=large ◦ force-=small ◦ Velocity=slow (take a lot of time, time=large) ◦ Velocity=fast (takes a little time, time=small) ◦ Power=force*velocity ◦ Power=force*velocity ◦ =small*small ◦ =large*large ◦ LITTLE POWER ◦ =A WHOLE LOT OF POWER ◦ Slower concentration contractions with a larger ◦ Faster concentration contractions produce less force than any type of slow contractions resistance produce greater force than any fast concentric contractions & slow concentric contractions with less resistance Power Final Statement ◦ Peak power occurs @ ◦ Intermediate level of velocity ◦ Beyond 30% of maximal velocity, power production decrease ◦ Intermediate level of muscle shortening & tension generation ◦ If not stretched beyond 70-80% of resting length, ability to develop contractile tension & exert force is essentially reduced to zero ◦ If stretched beyond 120-130% of resting length, significant decrease in the amount of tension a muscle can develop & amount of force a muscle can exert Injuries ◦ When training for flexibility, strength, endurance, & power, skeletal muscle can exhibit: ◦ Fatigue ◦ Strains ◦ Contusion ◦ Cramps ◦ DOMS ◦ Compartment Syndrome ◦ Cause of Fatigue: Fatigue ◦ Inconclusive, but postulations include: ◦ Reduction in rate of intracellular calcium release & ◦ An exercise-induced reduction in the maximal uptake by sarcoplasmic reticulum ◦ This is a major theory force capacity over time of muscle ◦ The opposite of endurance ◦ Increases in muscle acidity & intracellular potassium levels ◦ The more rapidly a muscle fatigues, the less ◦ Decreases in muscle energy supplies & intracellular endurance it has oxygen ◦ Fatigue may occur in: ◦ Characteristics of Fatigue ◦ The muscle fiber ◦ Reduction of muscle force production capabilities ◦ The motor unit itself (inhibiting ability to generate an action potential=no muscle twitch or contraction) ◦ Reduction of shortening velocity ◦ Prolonged relaxation of motor units between ◦ Variety of factors affect rate of fatigue of muscle recruitment ◦ Type & intensity if exercise ◦ Specific muscle groups involved in exercise ◦ Prolonged twitch duration ◦ Prolonged sarcolemma action potential of ◦ Physical environment in which the activity occurs reduced amplitude ◦ Muscle fiber type & pattern of unit activation Strains ◦ Overstretching of muscle tissue ◦ Magnitude of injury related to size of overload & rate of overloading ◦ Severity & symptoms of strain can be: ◦ Mild ◦ Minimal structural damage ◦ Feelings of tightness or tension in muscle ◦ Moderate ◦ Partial tear in muscle tissue ◦ Symptoms include pain, weakness, loss of function ◦ Severe ◦ Severe tearing of muscle ◦ Functional loss, accompanying hemorrhage, & swelling ◦ Most frequently strained muscle in human body: Hamstrings (lack of flexibility; 2 joint muscle-suffer passive insufficiency) Contusions Cramps ◦ Muscle bruises ◦ Include moderate to sever muscle spasms with proportional levels of ◦ Caused by: compression forces sustained during impacts accompanying pain ◦ Symptoms: hematomas within muscle ◦ Causes: ◦ Etiology is not well understood tissue ◦ Possible factors include: ◦ Can lead to development of much more serious condition called myositis ◦ Electrolyte imbalances ossificans, or calcification within the ◦ Deficiencies in calcium & magnesium muscle ◦ dehydration Compartment DOMS Syndrome ◦ Hemorrhage or edema within a muscle ◦ Delayed Onset Muscle Soreness (DOMS) compartment ◦ Occurs after some period of time followi◦ Caused by: injury or excessive muscular unaccustomed exercise exertion ◦ Arises 24-72 hours after participating in long strenuous bout of exercise (hints name ◦ Pressure increase within the compartment DELAYED, as it is not immediate) causing sever damage to neural & vascular ◦ Caused by: micro tearing of muscle tissue structures within compartments following the ◦ Symptoms include: absence of pressure release ◦ Same kind of histological change that ◦ Characterized by progressive: accompany acute inflammation ◦ Swelling ◦ Pain ◦ Discoloration ◦ Swelling ◦ Diminished distal pulse ◦ Reduced rang of motion ◦ Loss of sensation ◦ Loss of motor function Motor Units ◦ A motor nerve & all that it innervates or communicates with ◦ Depends on ◦ Signals the contraction of muscle fibers if ◦ The number of muscle fibers within each activated motor unit stimulus is adequate for each of the fibers ◦ Action potential ◦ The number of motor units activated ◦ All or none principle: ◦ To produce more force, the main method is to recruit more fibers to contract recruitment ◦ Regardless of number, individual muscle ◦ Recruitment: increase the number of fibers fibers within a given motor unit will either innervated fire & contract maximally or not at all ◦ Main muscular response used to produce greater muscle tension Fiber Composition of Motor Units ◦ Can have motor units with a lot or with a few fibers ◦ Very precise: ◦ Small motor unit ◦ A small number of fibers controlled by one motor unit ◦ Motor units that control eye movement ◦ Less precise: ◦ Large motor unit ◦ A large number of fibers controlled by one motor unit ◦ Quad muscle can have some 500 fibers in motor unit ◦ Motor nerve dictates what type of fiber a motor unit is Muscle Fibers ◦ All muscle contractions/actions are caused by muscle fibers ◦ Two types of fibers: ◦ Slow twitch ◦ Fast twitch Slow Twitch Muscle Fibers ◦ Slow Oxidative(SO) ◦ Build & decrease tension slowly ◦ Fuel source: oxidative phosphorylation ◦ Oxidative phosphorylation creates ATP ◦ Only one type of slow twitch muscle through the electron transport chain ◦ Slow oxidative (SO) ◦ Requires oxygen to create energy ◦ Characteristics ◦ Low strength of contraction ◦ Low anaerobic capacity ◦ Small in size ◦ High capillary density ◦ Highly resistant to fatigue ◦ Use: ◦ Actiivities that are done over a longer period of time but that doesn’t require a great deal of strength ◦ Running a marathon, hiking, walking, swimming long distance Fast Twitch Muscle Fibers • Build & decrease tension quickly • Two types: • Fast Glycolytic(FG) • Fast Oxidative & Glycolytic(FOG) ◦ Fast Oxidative & Glycolytic(FOG) ◦ Fast Glycolytic(FG) ◦ Energy source: hybrid ◦ Fuel source: Glycolysis ◦ Can use energy made fast without oxygen (anaerobic ◦ Glycolysis: energy pathway with 12 steps that gives off a pathway) lot of ATP quickly but also runs out quickly ◦ No oxygen required to create energy ◦ Can use energy made slowly with oxygen(aerobic pathway) ◦ Characteristics: ◦ Characteristics: ◦ High speed & strength of contraction ◦ High speed & strength of contraction ◦ Can use energy made aerobically & anaerobically ◦ High anaerobic capacity ◦ Intermediate sized fibers ◦ Largest of the 3 types of muscle fibers ◦ Low capillary density ◦ High capillary density ◦ Low aerobic capacity ◦ Fatigability varies ◦ More fatigable than SO ◦ Most easily fatigable ◦ Not as fatigable as FG ◦ Uses: ◦ Uses: ◦ Activities that are forceful & quick ◦ Depends on energy source ◦ Sprints, grabbing kid from in front of bus Fiber Composition & Training ◦ Cannot change fiber composition ◦ Fast twitch fibers to slow twitch fibers ◦ Slow twitch fibers to fast twitch fibers ◦ Can change fiber composition of ◦ Fast glycolytic fibers into fast oxidative & glycolytic fibers ◦ Fast oxidative & glycolytic fibers into fast glycolytic fibers ◦ Possible because all with in the fast twitch category ◦ The aerobic capacity & glycogen content of the muscle can be improve with training ◦ Done through specific training ◦ With distance ◦ Produce shift from FG to FOG fibers ◦ With weight training ◦ Produce shift from FOG to FG fibers Selective Recruitment ◦ Neurons tend to recruit smaller fiber types then larger fiber types ◦ Smallest output of force ◦ Slow oxidative (smallest) ◦ Fast oxidative & Glycolytic (slightly larger) ◦ Fast Glycolytic (largest) ◦ Largest output of force Factor Affecting Muscle Tension Development ◦ If summation/tetanus is reached, the force of the muscle contraction of fiber will increase accordingly, because of increased calcium available & a muscle contraction will occur ◦ Two types of muscle contraction ◦ Isometric: no movement (doing a plank) ◦ Isotonic: movement Contractions ◦ When tension is developed in a muscle ◦ Types of Contractions as a result of a stimulus ◦ To initiate or accelerate movement of a body segment ◦ Referred to as muscle action/ joint action ◦ Muscle contractions/actions can be ◦ To slow down or decelerate movement used to cause, control, or prevent joint of body segment movement ◦ To prevent movement of a body segment by external forces ◦ All muscle contractions/actions are either isometric or isotonic Types of Muscle Actions ◦ Isometric Contraction/Action ◦ Isotonic Contractions/Actions ◦ Active tension is developed within muscle ◦ Involve muscle developing active tension but joint angles remain constant to either cause or control joint movement ◦ Static contractions that prevent motion ◦ Dynamic contractions ◦ Significant amount of tension may ◦ The varying degrees of tension in muscles developed in muscle to maintain joint result in joint angles changing angle in relatively static or stable position ◦ Either concentric or eccentric ◦ May be used to prevent a body segment ◦ Concentric—shortening from being moved external forces ◦ Eccentric- lengthening Proprioceptors ◦ Mechanism by which the body is able ◦ Respond to changes in position & to regulate body position & movement acceleration of body segments by responding to stimuli subconsciously ◦ Provide feedback relative to the: & sending that information back to ◦ The position of the body & limbs brain ◦ Movement of joint ◦ These internal receptors are located: ◦ Multiple types of proprioceptors ◦ In the skin ◦ Two stimulated during muscle actions/contractions: ◦ In the inner ear ◦ In & around the joint, muscles, & tendons ◦ Musculotendinous receptors Musculotendinous Receptors ◦ Used in muscular control & coordination ◦ Provide feedback relative to the movements of the joint specifically: ◦ Tension within muscles ◦ Length of muscles ◦ Rate-of-change in length of muscles ◦ Contraction state of muscles ◦ Two Types: ◦ Golgi Tendon Organs (GTO) ◦ Muscle Spindal Golgi Tendon Organs (GTO) ◦ Signals ◦ Located in the tendons ◦ Afferent signals sent up spinal cord in response to ◦ Sensitive to tension development in tendons excessive contraction or passive stretch of tendons ◦ Due primarily to: ◦ Responding efferent signal has two purposes: ◦ Muscle contraction ◦ Inhibition (relaxation) of the contraction of the associate ◦ Passive stretch of tendon muscle (agonist) ◦ associated muscles’ antagoniste opposing muscle, the ◦ Golgi tendon keeps muscle from excessively contracting by ◦ When the Golgi Tendon signals fire, the result is ◦ Inhibiting the motor nerve (protective effect) ◦ Inhibition/relaxation of the agonist (working muscle) ◦ Excitation/contraction of the antagonist (associated ◦ Tension in tendons & GTO increases as muscle muscle) contractions, activating GTO ◦ GTO stretch threshold is reached ◦ Example: ◦ Impulse sent to CNS ◦ A weight lifter attempting an extremely heavy ◦ CNS sends signal to muscle to relax resistance in biceps curllifter reaches a point of ◦ Facilitates activation of antagonist as a protective extreme overload mechanism ◦ GTO activated ◦ Biceps suddenly relaxes/triceps suddenly contract appears as if lifter throwing weight down ◦ Really GTO has caused inhibition of biceps & contraction of triceps ◦ Signals ◦ Afferent signal sent up spinal cord in response to excessive stretch or rapid stretch Muscle Spindal ◦ Efferent sent in response to “stretch” has two purposes ◦ Located in muscle between the fibers ◦ Excitation & contraction of the associated muscle(agonist) ◦ Sensitive to ◦ Inhibition & relaxation of the associated muscles’ antagonist ◦ Degree in muscle strength ◦ Rate if muscle stretch ◦ Antagonist prevented from contracting ◦ When muscle spindal signals fire, the result is ◦ As you stretch a muscle ◦ Stretch of muscle spindals ◦ Contraction of the agonist (working muscle) ◦ Inhibition/relaxation of the antagonist (opposing ◦ Causes exited sensory nerves to send signal up spinal cord muscle) ◦ Examples ◦ CNS sends motor signal to cause a reflexive contraction of the associated ◦ Patellar tendon reflex muscle (agonist contracts) occurs ◦ Sudden tap on patellar tendon causes quick stretch of ◦ Called: Myotatic or Stretch Reflex musculotendinous units of quads ◦ Quick quad stretch activates muscle spindal ◦ Info sent to CNS to quickly contract quads ◦ Cause knee jerk Reciprocal Inhibition ◦ Two things can happen when muscle contracts: ◦ Sensory nerve excites agonist & inhibit agonist ◦ Caused by: Muscle Spindal ◦ Sensory nerves excites antagonist & inhibit agonist ◦ Caused by: Golgi Tendon Organs ◦ Either one occurring is called: Reciprocal Inhibition Fiber Length ◦ Another factor that affects the contraction of the ◦ If a sarcomere is stretched beyond its optimal muscle is the length of the muscle fiber before it is length, force output is virtually zero stimulated ◦ Lack of force production due to actin site blockage by myosin heads preventing new ◦ This length before stimulation & subsequent myosin tetanic tension is called length-tension relationship ◦ Theoretical optimal length of an intact muscle corresponds to muscle resting length ◦ Optimal length corresponds with maximum overlap of thick myosin filament & thin actin filament ◦ The elastic force contributed by elastic ◦ Tension optimized when max. number of active actin components changes optimal length for optimal sites are available force production ◦ If a sarcomere is stretched beyond optimal length, force output declines ◦ Decline occurs because thin filaments pulled away from thick filaments prevent myosin heads from binding Elastic Components ◦ Optimal resting length without series of ◦ Two types of elastic structures found with in components but because of passive tension musclotendon unit developed during motion, elastic components ◦ Parallel elastic component allow for greater tension as the muscle lengthens ◦ Series elastic component or passively stretches ◦ Series Elastic Component ◦ Elastic structures ◦ Passive elasticity derived from: tendons ◦ Non-contractile components of muscle ◦ The elastic component that lies in series (in line) ◦ Lay parallel to or in series with the contractile with the tendons & contractile structures (actin elements within muscle & tendons & myosin) ◦ Non-contractile muscle tissue stretched passively ◦ Provides resistive tension when muscles is ◦ Rather than by muscle contraction passively stretched ◦ Muscle tissues are NOT stretched by muscle contractio◦ If stretched, will spring back (recoil) stretched passively ◦ Tension between them prevent muscle damage that◦ Example: Box jumping could occur from external stretching forces ◦ Eccentric contraction followed by concentric contraction Length-Tension Relationship ◦ Maximal ability of a muscle to develop tension ◦ Generate greatest amount of tension can be & exert force varies depending upon: developed when a muscle is stretched between ◦ The length of the muscle during contraction 70-80% & 120-130% of its resting length ◦ Without elastic component/connective tissue ◦ The relationship between muscle length & muscle tension: ◦ Get most tension out of muscle @ resting length ◦ Shorter muscle=less tension ◦ With elastic component/connective tissue ◦ Generate greatest amount of tension can be ◦ Longer muscle=more tension developed when a muscle is stretched between 120- 130% of its resting level ◦ If not stretched beyond 70-80% of resting length ◦ Ability to develop contractile tension & exert force is essentially reduced to zero ◦ If stretched beyond 120-130% of resting length ◦ Significant decrease in the amount of tension a muscle can develop & amount of force a muscle can exert muscle articulation-biauriculate disadvantage ◦ Active & passive insufficiencies ◦ Active insufficiency ◦ Cannot contract(active) the same amount of ◦ Point reached when muscle becomes shortened to muscle tension or stretch(passive) with the same point it can no longer generate/maintain active amount of flexibility across two joints @ same time tension ◦ ONLY applies to 2 joint muscles ◦ Hamstring muscle ◦ NO insufficient with 1 joint muscle ◦ If shorten/contract across 1 jointhip ◦ Two types: ◦ Cannot keep shortening across other jointknee ◦ Muscle can only shorten/contract so much ◦ Active insufficiency ◦ Passive insufficiency ◦ Passive Insufficiency ◦ State reached with a muscle becomes stretched to point where it can no longer lengthen & allow movement ◦ Hamstring muscle ◦ If lengthen across one jointhip ◦ Cannot keep lengthening across another joint Force-Velocity Relationship ◦ The greater the load against which a ◦ Angle of Pull muscle must contract, the lower the ◦ @ 90˚=100% of muscle force contributes velocity of that contraction will be to movement of the bones ◦ Final player affecting force production ◦ Muscle is strongest @ 90˚ ◦ Muscle is weaker @ either end of 90˚ ◦ Most actions do not require you to hold muscle @ 90˚, so what happens to force production during different types of muscle contractions Muscle Tension • One of two situations occur: • Segment moves • Segment does not move ◦ Dynamic Tension(isotonic contraction) ◦ When the segment moves in the direction or • Two types of tension opposite to the direction of applied muscular • Dynamic tension(isotonic contraction) • Static tension(isometric contraction) tension ◦ Two types ◦ Concentric tension ◦ Static Tension(isometric contraction) ◦ Contraction of a muscle during which the muscle ◦ When a muscle produces tension or force against an shortens & causes movement towards the midline of opposing force or ressitance & the segment of muscle the body does not move ◦ Up movement of push up(tricep), down movement of push ups(bicep) ◦ Only one type: ◦ Eccentric tension ◦ Isometric tension ◦ Muscular contraction during which no discernible ◦ Contraction of muscle during which the muscle segmental movement is taking place lengthens & causes movement away from the midline of the body ◦ Muscles develop tension with no visible change in ◦ Down movement of pushup(tricep), up movement muscle length push up(bicep) ◦ Plank & wall squats, arm wrestling someone Force-Velocity Relationship cont. ◦ Static(isometric) contraction ◦ Concentric(isotonic) contractions ◦ Because static contraction occurs without muscle ◦ Slower speed (velocity) of concentric contraction- movement-velocity is not an issue more force ◦ Static contraction=more force than any ◦ Faster speed (velocity) of concentric contraction- concentric contration least force ◦ Staticce contraction cn develop more force than ◦ Probably due to: even the slowest concentric contraction ◦ High metabolic cost ◦ Due to: ◦ Faster the contraction= fewer cross-bridge ◦ Maximal cross-bridge interaction=max. force interactions(inability of some myosin cross-bridges to output bind with actin sites)= the loss of force production ◦ Myosin cross-bridges, without time constraints, attach freely to active actin sites o Eccentric (isotonic) contraction o Slower eccentric contraction- not as much force o Faster eccentric contraction-more force (up to a certain point) o Eccentric contractions, no matter velocity, can develop more force than ANY velocity concentric contractions & more than static o Due to: low metabolic cost elastic component, increasing # of active cross bridge Summary ◦ Amount of force generates listed from least to greatest: ◦ Faster concentric contraction ◦ Slower concentric contraction ◦ Static/isometic contraction ◦ Slower eccentric contraction ◦ Faster eccentric contraction ◦ Up to a point at which force production levels off Muscle Power ◦ Due to force force-velocity relationship, get maximum amount of force generation @ approx. 30% of maximal contraction velocity ◦ Beyond -30% of maximal velocity, force production decrease with increasing velocity ◦ Slow down amount of time spent on contraction(velocity of shortening) with any amount of force in order to produce greatest amount of power


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